U.S. president Donald Trump considers them a COVID-19 “game changer,” his top infectious diseases advisor says the evidence is flimsy, while ethicists worry pouring millions of the tablets into hospitals is a long shot that could make people sicker.

Two old anti-malaria medications are being pushed as potential treatments in the scramble to find something, anything, to neutralize the virus causing COVID-19.

Already, U.S. media are reporting a run on the drugs since Trump said they hold “tremendous promise.” In Nigeria, two people have overdosed after self-medicating with the pills, and Lagos State health authorities are urging against massive consumption of the tablets chloroquine and hydroxychloroquine.

There are concerns people could start hoarding the pills, the way many did with the anti-viral Tamiflu during the bird flu fright in 2005, and self-medicate in the hope of staving off the virus.

“You should not take medication without the scientific evidence,” Dr. Theresa Tam, Canada’s chief public health officer, said Monday. “These drugs are not without side effects. In fact, they have quite significant side effects.

One million doses of hydroxychloroquine are being donated to Canadian hospitals by Quebec-based JAMP Pharma Group. The company says its offer is twofold: to make the drugs available for people hospitalized with COVID-19, and to avoid a shortage of the pills for people who already need them to survive. Hydroxychloroquine, a less toxic version of chloroquine, is a common generic drug that’s used to treat lupus and rheumatoid arthritis, and lupus organizations are already reporting people are having problems filling prescriptions because of Trump’s exuberance. Those living with lupus are immune-compromised, putting them at greater risk of COVID-19.

Both drugs have shown activity against the virus that causes COVID-19 in vitro, meaning in tissue cultures. But some papers suggest the drugs can increase viral replication. “That is to say it can hurt you potentially,” said Dr. Anand Kumar, a critical care doctor at Winnipeg Health Sciences Centre, who is also trained in infectious diseases.

“There is the odd study that says these compounds could help, but there are just as many that fail to show any benefit and others that go the other way and suggest potential harm, Kumar said.

“Absolutely, it should be studied in a randomized trial, I have no problem with that. But the idea that people should start taking chloroquine because it’s a game-changer, I think is just nuts, frankly.”

Researchers at the University of Minnesota work with coronavirus samples as a trial begins to see whether malaria treatment hydroxychloroquine can treat COVID-19, March 19, 2020.Craig Lassig/Reuters

The drug is already being given to hospitalized COVID-19 patients on an “uncontrolled basis” in multiple countries, including the U.S., according to the U.S. Centers for Disease Control and Prevention. It’s one of several drugs under investigation in a mega trial sponsored by the World Health Organization — Solidarity — that’s looking at whether existing drugs can be repurposed to fight COVID-19.

But there’s no agreement on optimal dosing, and while the antimalarials are generally well tolerated in the healthy, it may not be true for the frail and the sick.

“It would be much better if the government could come up with a policy that said, for dying or severely compromised patients we will try some agents and we’ll do it in an organized manner so that we can figure out if anything helps and we don’t cause a slew of unexpected side effects,” said Dr. Arthur Caplan, head of the division of bioethics at NYU Langone Medical School. Caplan says the data from China is hyper-weak and “pouring zillions of pills into the world’s population achieves nothing but risking side-effects, at present.”

Outside of randomized controlled trials, several of which are underway in Canada, including to test whether hydroxychloroquine could prevent infections in frontline health-care workers, Kumar said the pills might be used as “salvage” therapy, when doctors have nothing left. “But frankly, the probability of it being useful in that situation is extremely low, slim to zero.”

In every single pandemic, everybody has hundreds of solutions they think might work

One theory is that the drug may dampen down an over-exuberant cytokine storm. Normally when exposed to a virus, the body stimulates the immune cells to produce chemicals to throw off the invader. But the cells can become so hyper-stimulated they start attacking the self, your own tissue.

Other contenders include Gilead Sciences’ Remdesivir, which Trump also mentioned last week. The drug has been given to hundreds of infected people in the U.S., Europe and Japan on an emergency access basis. Demand has flooded the company’s emergency treatment access system, which was never set up to handle a pandemic. The company has temporarily halted access while it pivots to a new system.

“If it works well, and that’s a big if, that could be a game-changer,” Kumar said. However a similar drug was used years ago in SARS and failed, because toxicity was too great.

“In every single pandemic, everybody has hundreds of solutions they think might work,” Tam said. “We can’t rule out the fact they don’t work, but let’s prioritize the top ones that world scientists think are important and do proper trials.”